Stevens was born on April 20, 1920, in Hyde Park,[6]Chicago, Illinois, to a wealthy family.[4] His paternal grandfather had formed an insurance company and held real estate in Chicago, while his granduncle owned the Chas A. Stevens department store. His father, Ernest James Stevens (1884-1972), was a lawyer who later became a hotelier, owning two hotels, the La Salle and the Stevens Hotel. He lost ownership of the hotels during the Great Depression and was convicted of embezzlement (the conviction was later overturned).[4] (The Stevens Hotel was subsequently bought by Hilton Hotels and is today the Chicago Hilton and Towers.) His mother, Elizabeth Maude (Street) Stevens (1881-1979), was a high school English teacher. Two of his three older brothers also became lawyers.

Stevens married Elizabeth Jane Shereen in June 1942. Divorcing her in 1979, he married Maryan Mulholland Simon that December. He has four children: John Joseph (who died of cancer in 1996), Kathryn, Elizabeth, and Susan.

Given his stellar academic performance in law school, several prominent Northwestern faculty members recommended Stevens for a Supreme Court clerkship: he served as a clerk to Justice Wiley Rutledge during the 1947–48 term[4] (This service, Stevens has said, deeply inspired him, as evident from his Rutledgean focus on the careful interpretation of the facts in a case present in his opinions).

Following his clerkship, Stevens returned to Chicago and joined the law firm of Poppenhusen, Johnston, Thompson & Raymond (which, in the 1960s, would become Jenner & Block). Stevens was admitted to the bar in 1949. He determined that he would not stay long at the Poppenhusen firm after he was docked a day's pay for taking the day off to travel to Springfield to swear his oath of admission. During his time at the Poppenhusen firm, Stevens began his practice in antitrust law.

In 1951, he returned to Washington, D.C. to serve as Associate Counsel to the Subcommittee on the Study of Monopoly Power of the Judiciary Committee of the U.S. House of Representatives. During this time, the subcommittee worked on several highly publicized investigation concerns in many industries, most notably Major League Baseball.

In 1952, Stevens returned to Chicago and, together with two other young lawyers he had worked with at the Poppenhusen firm, formed his own law firm, Rothschild, Stevens, Barry & Myers. They soon developed a successful practice, with Stevens continuing to focus on antitrust cases. His growing expertise in antitrust law led to an invitation to teach the "Competition and Monopoly" course at the University of Chicago Law School, and from 1953 to 1955, he was a member of the Attorney General's National Committee to Study Antitrust Laws. At the same time, Stevens was making a name for himself as a first-rate antitrust litigator and was involved in a number of trials. He was widely regarded by colleagues as an extraordinarily capable and impressive lawyer with a fantastic memory and analytical ability, and authored a number of influential works on antitrust law.[10]

In 1969, the Greenberg Commission, appointed by the Illinois Supreme Court to investigate Sherman Skolnick's corruption allegations leveled at former Chief Justice Ray Klingbiel and current Chief Justice Roy J. Solfisburg, Jr., named Stevens as their counsel, meaning that he essentially served as the commission's special prosecutor.[4] The Commission was widely thought to be a whitewash, but Stevens proved them wrong by vigorously prosecuting the justices, forcing them from office in the end.[11] As a result of the prominence he gained during the Greenberg Commission, Stevens became Second Vice President of the Chicago Bar Association in 1970.

President Gerald Ford then nominated him as an Associate Justice of the Supreme Court in 1975 to replace Justice William O. Douglas, who had recently retired, and he took his seat December 19, 1975, after being confirmed 98–0 by the Senate.

When Harry Blackmun retired in 1994, Stevens became the senior Associate Justice and thus assumed the administrative duties of the Court whenever the post of Chief Justice of the United States was vacant or the Chief Justice was unable to perform his duties. Stevens performed the duties of Chief Justice in September 2005, between the death of Chief Justice William Rehnquist and the swearing-in of new Chief Justice John Roberts, and presided over oral arguments on a number of occasions when the Chief Justice was ill or recused. Also in September 2005 Stevens was honored with a Symposium by Fordham Law School for his 30 years on the Supreme Court, and President Ford wrote a letter stating his continued pride in appointing him.[12][13]

In a 2005 speech, Stevens stressed the importance of "learning on the job"; for example, during his tenure on the Court, Stevens changed his views on affirmative action (initially opposed), as well as on other issues.[14] President Ford praised Stevens in 2005: "He is serving his nation well, with dignity, intellect and without partisan political concerns."[15]

As his seniority grew in the closing decade of the Rehnquist court, Stevens was often the senior justice on one side of a split decision and thereby entitled to assign the writing of the opinion. He almost always wrote a dissenting opinion when in dissent and wrote concurring opinions more often than most other justices historically.[citation needed] Additionally, he participated actively in questioning during oral arguments.[5] Stevens was elected a Fellow of the American Academy of Arts and Sciences in 2008.[16]

Stevens retired as the third-longest-serving justice in the history of the Court with 34 years, six months service. The longest-serving is his immediate predecessor, Justice William O. Douglas, who served 36 and a half years. Stevens is also the second-oldest justice, aged 90 years and two months at retirement, in the Court's history behind Oliver Wendell Holmes, Jr., who retired at the age of 90 years and 10 months. In July 2015, Stevens became the longest-lived retired justice, surpassing Stanley Forman Reed, who died at age 95 years and 93 days.

On June 26, 2015, Stevens attended the Court's announcement of the opinion in Obergefell v. Hodges,[20] in which the Court held that state recognition of same-sex marriage is a constitutional right under the Fourteenth Amendment.

When he was appointed to the Supreme Court, Stevens was a registered Republican.[21] Asked in an interview in September 2007 if he still considers himself a Republican, Stevens declined to comment.[22]

Stevens's jurisprudence has usually been characterized as idiosyncratic. Stevens, unlike most justices, usually wrote the first drafts of his opinions himself and reviewed petitions for certiorari within his chambers instead of having his law clerks participate as part of the cert pool. He is not an originalist (such as fellow Justice Antonin Scalia) nor a pragmatist (such as Judge Richard Posner), nor does he pronounce himself a cautious liberal (such as Justice Ruth Bader Ginsburg). He was considered part of the liberal bloc of the Court starting in the mid-1980s, and was dubbed the "Chief Justice of the Liberal Supreme Court",[27][28] though he publicly called himself a judicial conservative in 2007.[29][30]

Stevens wrote the majority opinion in Hamdan v. Rumsfeld in 2006, in which he held that certain military commissions had been improperly constituted. He also wrote a lengthy dissenting opinion in Citizens United v. FEC, arguing the majority should not make a decision so broad that it would overturn precedents set in three previous Supreme Court cases.

Stevens's views on obscenity under the First Amendment have changed over the years. Initially quite critical of constitutional protection for obscenity, rejecting a challenge to Detroit zoning ordinances that barred adult theaters in designated areas in 1976's Young v. American Mini Theatres, 427U.S.50 (1976), ("[E]ven though we recognize that the First Amendment will not tolerate the total suppression of erotic materials that have some arguably artistic value, it is manifest that society's interest in protecting this type of expression is of a wholly different, and lesser, magnitude than the interest in untrammeled political debate"), Stevens now adheres firmly to a libertarian free speech approach on obscenity issues, voting to strike down a federal law regulating online obscene content considered "harmful to minors" in 2002's ACLU v. Ashcroft, 535U.S.564 (2002), which in a dissenting opinion Stevens argued that while "[a]s a parent, grandparent, and great-grandparent", he endorsed the legislative goal of protecting children from pornography "without reservation": "As a judge, I must confess to a growing sense of unease when the interest in protecting children from prurient materials is invoked as a justification for using criminal regulation of speech as a substitute for, or a simple backup to, adult oversight of children's viewing."[31]

Perhaps the most personal and unusual feature of his jurisprudence is his continual referencing of World War II in his opinions, which Stevens often cites in an attempt to appeal to shared patriotic, American values. For example, Stevens, a World War II veteran, was visibly angered by William Kunstler's flippant defense of flag-burning in oral argument in 1989's Texas v. Johnson, 491U.S.397 (1989) and voted to uphold a prohibition on flag-burning against a First Amendment argument. Wrote Stevens, "The ideas of liberty and equality have been an irresistible force in motivating leaders like Patrick Henry, Susan B. Anthony, and Abraham Lincoln, schoolteachers like Nathan Hale and Booker T. Washington, the Philippine Scouts who fought at Bataan, and the soldiers who scaled the bluff at Omaha Beach. If those ideas are worth fighting for – and our history demonstrates that they are – it cannot be true that the flag that uniquely symbolizes their power is not itself worthy of protection from unnecessary desecration."

In Wallace v. Jaffree, 472U.S.38 (1985), striking down an Alabama statute mandating a minute of silence in public schools "for meditation or silent prayer", Stevens wrote the opinion for a majority that included Justices William Brennan, Thurgood Marshall, Harry Blackmun, and Lewis Powell. He affirmed that the Establishment Clause is binding on the States via the Fourteenth Amendment, and that: "Just as the right to speak and the right to refrain from speaking are complementary components of a broader concept of individual freedom of mind, so also the individual's freedom to choose his own creed is the counterpart of his right to refrain from accepting the creed of the majority. At one time, it was thought that this right merely proscribed the preference of one Christian sect over another, but would not require equal respect for the conscience of the infidel, the atheist, or the adherent of a non-Christian faith such as Islam or Judaism. But when the underlying principle has been examined in the crucible of litigation, the Court has unambiguously concluded that the individual freedom of conscience protected by the First Amendment embraces the right to select any religious faith or none at all."

Stevens wrote a dissent in Van Orden v. Perry, 545U.S.677 (2005), which was joined by Justice Ginsburg; he argued that the ten commandments displayed in the Texas Capitol grounds transmitted the message: "This State endorses the divine code of the 'Judeo-Christian' God." The Establishment Clause, he wrote, "at the very least [...] has created a strong presumption against the display of religious symbols on public property", and that it "demands religious neutrality – Government may not exercise preference for one religious faith over another". This includes a prohibition against enacting laws or imposing requirements that aid all religions as against unbelievers, or aid religions that are based on a belief in the existence of God against those founded on different principles.

In a 2009 paper[32]Ward Farnsworth argues that Stevens's "dissents against type" (in Stevens's case, votes in dissent in favor of the government's position and against the accused, such as the one in Kyllo) suggest that while Stevens "believes strongly in laying out resources for the sake of accuracy and opportunities to protest an unfair trial, [he is] not nearly as concerned about restraining the government at the front end of the process, when it is gathering evidence – for the costs of invaded rights then are to liberty rather than to accuracy".

Stevens joined the majority in Gregg v. Georgia, 428U.S.153 (1976), which overruled Furman v. Georgia, 408U.S.238 (1972) and again allowed the use of the death penalty in the United States. In later cases such as Thompson v. Oklahoma, 487U.S.815 (1988) and Atkins v. Virginia, 536U.S.304 (2002), Stevens held that the Constitution forbids the use of the death penalty in certain circumstances. Stevens opposed using the death penalty on juvenile offenders; he dissented in Stanford v. Kentucky, 492U.S.361 (1989) and joined the Court's majority in Roper v. Simmons, 543U.S.551 (2005), overturning Stanford. In Baze v. Rees, 553U.S.35 (2008), Stevens voted with the majority in upholding Kentucky's method of lethal injection because he felt bound by stare decisis. However, he opined that "state-sanctioned killing is...becoming more and more anachronistic" and agreed with former Justice Byron White's assertion that "the needless extinction of life with only marginal contributions to any discernible social or public purposes...would be patently excessive" in violation of the Eighth Amendment (quoting from White's concurrence in Furman).[33][34] Soon after his vote in Baze, Stevens told a Sixth Circuit conference that one of the drugs (pancuronium bromide) in the three-drug cocktail used by Kentucky to execute death row inmates is prohibited in Kentucky for euthanizing animals. He questioned whether Kentucky Derby second-place finisher Eight Belles died more humanely than those on death row.[35] He explained that his death penalty decisions were influenced, in part, by an increasing awareness through DNA testing of the fallibility of death sentences, and the fact that death-qualified juries come with a set of biases.[36] Stevens, at the time of his opinion in Baze, was one of four Justices (the others being Brennan, Marshall and Blackmun) who had concluded that post-Gregg capital punishment is unconstitutional under the Eighth Amendment.[37] After his retirement, Stevens stated that his vote in Gregg was the only vote he regretted.[38]

Stevens authored the majority opinion in Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., 467U.S.837 (1984).[39] The opinion stands for how courts review administrative agencies' interpretations of their organic statutes. If the organic statute unambiguously expresses the will of Congress, the court enforces the legislature's intent. If the statute is unclear (and is thus thought to reflect a Congressional delegation of power to the agency to interpret the statute), and the agency interpretation has the force of law, courts defer to an agency's interpretation of the statute unless that interpretation is deemed to be "arbitrary, capricious, or manifestly contrary to the statute". This doctrine is now generally referred to as "Chevron deference" among legal practitioners.[40]

Stevens wrote the lead opinion in Crawford v. Marion County Election Board, a case where the Court upheld the right of states to require an official photo identification card to help ensure that only citizens vote. Chief Justice Roberts and Justice Kennedy joined this opinion, and Justices Scalia, Thomas, and Alito agreed with them on the outcome. Edward B. Foley, an election law expert at Ohio State University, said the Stevens opinion might represent an effort to "depoliticize election law cases".[41] Stevens's vote in Crawford and his agreement with the Court's conservative majority in two other cases during the 2007–2008 term (Medellin v. Texas, 552U.S.491 (2008) and Baze v. Rees) has led University of Oklahoma law professor and former Stevens clerk Joseph Thai to wonder if Stevens is "tacking back a little bit toward the center".

In Bush v. Gore, 531U.S.98 (2000), Stevens wrote a scathing dissent on the Court's ruling to stay the recount of votes in Florida during the 2000 presidential election. He believed that the holding displayed "an unstated lack of confidence in the impartiality and capacity of the state judges who would make the critical decisions if the vote count were to proceed". He continued, "The endorsement of that position by the majority of this Court can only lend credence to the most cynical appraisal of the work of judges throughout the land. It is confidence in the men and women who administer the judicial system that is the true backbone of the rule of law. Time will one day heal the wound to that confidence that will be inflicted by today's decision. One thing, however, is certain. Although we may never know with complete certainty the identity of the winner of this year's Presidential election, the identity of the loser is perfectly clear. It is the Nation's confidence in the judge as an impartial guardian of the rule of law."

Stevens, his head at least, appears in Futurama S5 Episode 4, "A Taste of Freedom". He is brought out with other Supreme Court Justices during the case, Earth v. Zoidberg.

According to an April 2009 article in the Wall Street Journal, Stevens "rendered an opinion on who wrote Shakespeare's plays," proclaiming himself an Oxfordian." That is, he believes the works ascribed to William Shakespeare actually were written by Edward de Vere, 17th Earl of Oxford.[42] As a result, he was appointed Oxfordian of the Year by the Shakespeare Oxford Society.[43] According to the article, Justices Scalia and Blackmun shared Stevens's belief.[42]

^Rosen, Jeffrey (September 23, 2007). "The Dissenter, Justice John Paul Stevens". The New York Times. Retrieved April 11, 2010. I asked whether he still considers himself a Republican. "That's the kind of issue I shouldn't comment on, either in private or in public!" he said with a smile.